German Published Patent Application No. 35 31 198 discloses a system for controlling an internal combustion engine. It describes a method and a device for controlling a self-ignitible internal combustion engine with a fuel pump, a speed sensor, and a gas-pedal position sensor. A controlling unit, which determines the quantity of fuel to be injected, is triggered dependent upon various signals. The described system comprises a very complex monitoring system. Upon recognition of an emergency situation, the injected fuel quantity is reduced to a specified value. This complex monitoring system makes it possible to guarantee that, even if some of its components fail, no critical operating states, which would destroy the internal combustion engine, are attained. However, this system has the disadvantage that only a very limited operation is possible when an emergency situation is recognized. All that is guaranteed is that the driver is able to drive to the nearest service station.
Problems also arise in such a system because errors also occur in the monitoring system. As a result, the danger of switching to emergency operation on a very frequent basis exists, which means that only a very limited driving operation remains possible.
The object of the present invention is to improve the availability of a system for controlling an internal combustion engine to maintain smooth operation under emergency conditions, even if various sensors or the control unit should fail.